my 1978 uses
1/2 inch, too. My chainplate bolts are 7/16 x either 1 or 1/4. with the bulkheads, depending upon the way your current bulkheads are shaped, you might need to round off the edges (a 1/4 inch round router bit or more) so that they will fit into the channels and alongside the setees. also, remember that the old ones are glassed to the hull, so take along something to cut out the old ones (a rotozip works pretty well but you eat up the bits) and some epoxy and some 4 inch fiberglass tape. ---- edit: try your best to save the old ones as templates. If the bottoms are all rotted out, take along some cardboard, a utility knife, a pen, a heavy duty stapler with staples at least 1/2 inch long, and some rough sandpaper on a sanding block. cut a rough shape out of the cardboard, 1 or 2 feet long, marking the bulkhead where that piece will go. Mark high spots on the cardboard, and then knock them down smooth with the rough sandpaper. Test the fit, mark, shape, test, mark, etc. WHen you have it how you like it, staple that badboy to the bulkhead and make the next section. Of course, try to avoid knocking them off when you remove the bulkheads Also, you might consider taking a small hand grinder in case you need to very carefully knock the leftovers from the bulkhead fiberglass tabs flush-ish with the hull so that you can fit the new ones in easier and have a clean lay for you glass. Even if you don't sand those fiberglass tabs down, take a mask, some goggles, a long sleeve shirt and pants, and some glove. A shop vac and an assistant helps keep the dust down too.
